1. Field of the Invention
The present invention concerns a gasket element for the covering cap of a tubular writing pen of the type having a sleeve body enclosure, an ink reservoir and a capillary channel extending into a tubular writing element. The gasket is in the form of a cup-shaped element consisting of elastic material which has an upper annular sealing surface as a sealing support for the front edge of the sleeve body and writing socket beyond which extends the writing element.
Such gasket elements for pen quivers or pen covering caps, respectively, are generally known. A gasket element inserted into a covering cap is described in West German Utility Pat. No. 1,935,398 consists of an elastic material and has essentially the shape of a cup, so that the upper extremity is cylindrical and defines an upper edge forming an annular sealing surface which is in contact with the front edge of the sleeve body surrounding the writing socket, as the tubular pen is tightly screwed or inserted into the covering cap.
However, in the case of tubular writing pens, not only the area between the sleeve body and writing socket, for example, the outlet area of an ink equalizing chamber, should be sealed off against the surrounding air. Simultaneously, also, the tubular writing element should be sealed off. However, it has been determined that, when utilizing a cup-shaped gasket element effective sealing of the writing element could not be achieved in the long run. In order to achieve a sufficient dual sealing effect, the front end of the tubular writing element must be pushed against the bottom surface of the cup-shaped element with a certain pressure, so that his bottom surface elastically deforms and rests tightly against the front end of the tubular writing element giving a sealing effect. Very frequently, this resulted in penetration into the material of the bottom surface by the tubular writing element and resultant damaging of the bottom surface which actually impaired the sealing effect.
Another problem arises particularly in the case of tubular pens for extremely low widths of lines, e.g. about 0.1 mm, since, in the case of these tubular pens, the tubular writing elements are very thin and can be bent simply by means of the load resulting from the pressing of the tubular writing element upon the bottom surface of the cup-shaped element.
Finally, tubular pens for different widths of lines have specific deviations in their dimensions which can amount up to .+-. 1 mm in extreme cases. If a gasket element of a certain dimension would be used for all these tubular pens, it is quite obvious that then there would be no sealing effect at all at the tubular writing element in the case of some tubular pens and/or, in the case of other tubular pens, the tubular writing elements would penetrate into the material of the bottom surface of the gasket element or the tubular writng element would be bent or broken off.